/Engine/Source/Runtime/Engine/Classes/PhysicsEngine/SphereElem.h
Finds the closest point on the shape given a world position. Input and output are given in world space
The distance between WorldPosition and the shape. 0 indicates WorldPosition is inside the shape.
float GetClosestPointAndNormal ( const FVector & WorldPosition, const FTransform & BodyToWorldTM, FVector & ClosestWorldPosition, FVector & Normal ) const